In communication systems such as ad hoc radio systems, channel measurements are utilized for route selection based on link quality, spatial use of radio resources, interference avoidance, and rate and power control, among others. In ad hoc radio systems where the control and the data channels occupy a same band and are frequently interleaved in time with one another, channel measurements can be readily accomplished. In ad hoc radio systems, channel measurements can be made on a variety of transmission types, for instance, in IEEE (Institute of Electrical and Electronics Engineers) 802.11 systems, an exchange of request-to-send (RTS) and clear-to-send (CTS) messages can be used to estimate the quality of the channel.
Next generation ad hoc wireless communication networks may include data and control channels in separate physical channels (frequencies) located in separate frequency bands (e.g., 2.4 GHz and 5.7 GHz, respectively) to increase the overall data channel capacity. However, in such radio systems, the process of obtaining data channel measurements can be more complex than in current systems. For example, choosing the correct rate for an initial packet exchange between two nodes, or optimizing a resource allocation based on each link's particular condition may be more challenging when the control signaling is carried out in a first frequency band while the data communications take place in a second frequency band. This is because it is common for nodes in peer-to-peer systems to estimate the quality of the link between them by taking measurements of control messages such as the RTS and CTS messages.
One possible solution for measuring the data channel in such ad hoc radio systems would be to have nodes receive and measure the preambles and headers of packets transmitted on the data channel and destined to both themselves and other nodes. In this way, a node may gather information about the channel between itself and other nodes in the system. However, receiving numerous packets on a wideband data channel for the mere purpose of performing channel measurement/estimation is an inefficient use of a device's battery. In addition, this solution would not guarantee that link measurements would be available before a data exchange begins. Further, this solution would prove ineffective in radio systems employing Orthogonal Frequency Division Multiple Access (OFDMA), which allows multiple nodes to transmit simultaneously using only portions of the bandwidth. In these cases, channel measurements taken on data transmissions may not be available for the entire bandwidth of the data channel and thus may not be useful for determination of initial rate and power control. A full band measurement is especially critical when operating in very wide band channels (e.g. 80 MHz) as the fading and interference may vary across the channel. So, measuring only a portion of the channel could result in a node using either an overly optimistic or overly pessimistic channel measurement.
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